Fuel control and ignition system



Aug. 30, 1966 L. v. M CARTY ETAL 3,269,447

FUEL CONTROL AND IGNITION SYSTEM Filed Jan. 16, 1964 \NVENTORS ARTY quezevea fig-(c2265 ATToRNEv LQURDES \l. M C Laweeuce BY/CZHFFORD 4 3,269,447 Ce Patented August 30, 1966 3,269,447 FUEL (CONTRUL AND IGNITION SYSTEM Lourdes V. McCarty, Lawrence Queever, and Clifford Hotchiriss, all of Milwaukee, Wis, assignors to Controls Company of America, Melrose Park, llL, a corporation of Delaware Filed Jan. 16, 1964, Ser. No. 338,259 9 Claims. (Cl. 158-28) This invention relates to ignition systems and, more particularly, to a combination fuel control and ignition system.

The supply of fuel to a burner when the ignition system is disabled and incapable of igniting the fuel creates a potentially hazardous condition by placing a large amount of unignited fuel in the burner area. One type of fuel control and ignition system which has been proposed as a possible solution to this problem has taken advantage of the characteristic that after a solenoid controlled valve (used in many fuel systems) is opened the valve can be held open by reducing the voltage on the valve below that necessary to open the valve. This reduced voltage is capable of holding the valve open but is incapable of re-opening the valve should it close due, for example, to a power failure of short duration. However, such prior systems have not been completely satisfactory in that they have required relatively expensive components, eg power transformers to effect ignition and also to limit current flow to the valve after ignition, and/or these systems have been relatively complex requiring various switching and control arrangements which, in addition to adding to complexity of the control, add to its cost.

This invention is concerned with this type of fuel control and ignition system, namely one including an electrically operated control mechanism characterized by being capable of maintaining fuel flow with a reduced voltage once flow has been initiated, and has as a general object to simplify and reduce the cost of control systems of this type while providing a more positive control from a safety standpoint.

For the achievement of this and other objects, this invention proposes to utilize a control system having a flow control valve mechanism which is ineffective to initiate fuel flow when subjected to line voltage alone. The control system also includes means for increasing the voltage on the valve mechanism when burner operation is called for, but is rendered ineffective after ignition to return the system to the condition wherein only line voltage is applied to the valve mechanism. Line voltage, although insuflicient to open the valve initially, is suificient to hold the valve open. The control system is further constructed and arranged so that, in the event that the burner is extinguished due to an interruption of insufficient duration to re-set the circuit for ignition, the voltage increasing means remains inactive and the control valve, which will have closed during the interruption, will remain closed and no fuel flow occurs. This type of control operation permits a relatively simple and economical control construction and, consistent with the provision of a simple and economical fuel control system, this invention also contemplates a simple, economical and yet effective ignition system so as to preserve the simplicity and economy provided by the fuel control system.

Other objects and advantages will be pointed out in, or be apparent from, the specification and claims, as will obvious modifications of the embodiments shown in the drawings, in which:

FIG. 1 is an electric circuit diagram of a combination fuel control and ignition system constructed in accordance with this invention;

FIG. 2 illustrates an alternative ignition system;

FIG. 3 illustrates another alternative ignition system; and

FIG. 4 illustrates still another alternative ignition system.

With particular reference to the drawings, a control system constructed in accordance with this invention is illustrated as including fuel control portion 10 and ignition portion 12 comprising spark gap 14 and control circuit 16 enclosed by the dotted lines in FIG. 1. In the illustrated embodiment, both the fuel control and ignition portions are energized from a suitable A.C. source 18 through line leads L and L Turning first to the fuel control portion, it includes. an electrically operated fuel flow control valve 20, such as a solenoid controlled valve, which is connected to control flow in a fuel line in a manner well known in the art and not shown. For convenience only the operating coil and plunger of the valve have been illustrated. As has been recognized in the art, solenoid controlled valves exhibit an opening voltage and a holding voltage (i.e. the voltage necessary to hold the valve open), the holding voltage being lower than the opening voltage so that, once the valve has been opened to initiate the fuel flow, the voltage can be reduced and still maintain fuel flow. The fuel control portion also includes a transformer 22 which is associated with valve 21) in a manner to increase the voltage applied to the valve to effect valve opening. With such an arrangement of solenoid valve and transformer, the circuit elements can be selected so that valve 20 will not open when subjected to line voltage, the voltage from A0. source 18, alone but transformer 22, when energized, will increase the voltage on th valve suflicient to open the valve. More particularly, transformer 22 is connected with its primary coil 24 across source 18 and with its secondary coil 26 in series circuit relationship with operating coil 21 of valve 26 With this arrangement, fuel control portion 10 includes two circuit branches A and B arranged in parallel circuit relationship, one circuit branch including primary 24 and the other circuit branch including, in series circuit relationship, the operating coil of valve 20 and the secondary coil of the transformer 22. When heat is called for, line voltage (that across L and L is applied to valve 2t} and simultaneously transformer 22 is energized so that its secondary voltage is additive with the line voltage to achieve a voltage across valve 20 sufiicient to open it. With the valve open, fuel flows to the burner (not shown) where it is ignited when ignition portion 12 produces a spark across gap 14.

Flame sensor 28 is connected in the circuit of the fuel control portion and is arranged to respond to the flame produced as a result of ignition. The flame sensor can be of any suitable well-known construction and, similarly, it can be arranged for response to the flame, or heat of the flame, in a manner well known in the art. As illustrated, electrically the flame sensor is arranged in the circuit branch including primary 24 of the transformer. After ignition occurs, in a manner to be described more completely hereinafter, the flame sensor operates to open the circuit to the transformer primary, and it will be noted that as illustrated opening flame sensor 28 also de-energizes the ignition portion. This de-energizes the transformer and reduces the voltage on coil 21 to line voltage alone, which is suflicient to hold the valve open but is insufficient to re-open the valve should it close. As an example of the safety provided by this circuit arrangement, after ignition the valve is held open by a reduced voltage and continues to supply fuel to the burner as long as heat is called for, also during this period the ignition portion of the system is de-energized. If a momentary power failure should occur which Would allow the valve to close and extinguish the burner but is of a duration insufficient to permit the system to re-set itself for ignition, i.e. to allow the flame sensor to cool sufiiciently to reestablish circuits to the transformer primary and the ignition portion, valve is only subjected to line voltage so it remains closed preventing fuel flow and preventing the creation of the potentially hazardou condition of having excess fuel in the burner area. It will be appreciated that the line voltage referred to throughout this application is intended to cover any source of A.C. used to provide current flow in the system.

It should be noted that, although the primary winding of the transformer is removed from the active circuit of the fuel control portion, its secondary remains in circuit with coil 21 and will act in the nature of an impedance to thereby further reduce the voltage on the valve and insure that the valve will not be opened.

Turning now to ignition portion 12, control circuit 16, associated with spark gap 14, is effective to pulse the spark gap with a voltage sufiicient to draw an are between electrodes 14a and 14b for ignition purposes. More particularly, control circuit 12 includes a voltage step-up transformer 32 arranged with its secondary coil 34 connected in circuit with gap 14. In this instance, one end of coil 34 is connected to electrode 14b and its other end and electrode 14a are connected to ground. Primary winding 36 of the transformer is connected in series circuit relationship with capacitor 38 and both are connected across A.C. source 18. A shunt circuit 40, including switch 42, is arranged across capacitor 38 and primary winding 36 so that when closed, it completes a circuit including capacitor 38 and coil 36. In the particular embodiment illustrated in FIG. 1, switch 42 is a normallyopen switch associated with a suitable motor, shown schematically as coil 44, which is effective to close the switch with a predetermined time delay after heat has been called for and valve 20 opened. During the time delay a charge accumulates on capacitor 38 through rectifier 46 and resistance 48 and will reach a preselected value by the time that switch 42 is closed. When switch 42 is closed the charge stored on the capacitor is discharged through primary coil 36 inducing a sufficiently high voltage in secondary coil 34 to break down the spark gap and draw an arc.

A safety lockout is also provided for de-energizing the valve to terminate fuel flow should ignition fail to occur and comprises a thermally responsive switch 27 and a heater 29. Heater 29 is connected in the circuit branch containing primary coil 24, whereas, switch 27 is connected between that circuit branch and the branch containing the operating coil of valve 20 and secondary coil 26 of the transformer. It will also be noted that switch 27 is arranged to control energization and de-energization of the ignition portion of the system. Heater 29 is thermally related with switch 27 so that prolonged current flow through the heater will open the switch after a time delay. Should the system be energized and ignition not occur so that flame sensor 28 does not operate, current flow through heater 29 eventually opens switch 27 thereby deenergizing and closing valve 20 and de-energizing the ignition portion. With the illustrated arrangement heater 29 remains connected across the A.C. sources and prevents an excessive amount of fuel being delivered to the burner without ignition until the defect preventing ignition is detected.

To summarize the operation of the control system of FIG. 1, when heat is called for line voltage is applied to valve 20 and a charge begins to accumulate on capacitor 38. Transformer 22 is also energized and the voltage it produces is added to line voltage to operate valve 26 and initiate fuel flow. After a predetermined time delay to insure delivery of sufficient fuel to the burner and buildup of an adequate charge on capacitor 38 for ignition purposes, motor 44 closes switch 42 and capacitor 38 discharges through coil 36 of transformer 32 which in turn breaks down gap 14 and draws an are between electrodes 14a and 14b. Flame sensor 23 will operate subsequent to successful ignition and open the circuit to both the transformer primary and the ignition portion, leaving valve operating coil 21 energized through secondary coil 26 and by line voltage alone. Should valve 20 close momentarily to extinguish the burner without allowing suflicient time for the flame sensor to cool and re-set the circuit for ignition (e.g. by reason of a temporary power failure), valve 20 will only be subjected to line voltage which is insuflicient to open the valve and, hence, no fuel flows to the burner. Under normal operation, the valve will have remained open until heat was no longer called for whereupon the valve would be closed by removing line voltage through operation, for example, of a control thermostat (not shown). If ignition does not occur when heat is called for, the safety lockout will eventually close the valve and de-energize the ignition portion.

The fuel flow control and ignition portions of the system of this invention provide a particularly simplified and economical, and yet effectively operating, construction. It will be appreciated that various modifications can be made in the circuit arrangement illustrated in FIG. 1 without departing from the true spirit and scope of this invention. The operating and holding voltages of the valve will, of course, depend upon the particular valve used and, similarly, the voltage to be supplied by the transformer is dependent upon the valve used and the line voltage available. These factors will vary in accordance with the particular application, however, the basic operating principle will be retained, namely increasing the voltage on the valve above that normally applied (line voltage) so as to effect valve opening and, after the valve is opened, holding the valve open with the voltage reduced to normal. Because of the many variations possible within this operating principle, no single example of source voltage, operating and holding voltages and transformer is given nor is one believed to be necessary.

The fuel flow control portion of this system lends itself well to use with variations of the ignition portion discussed above. More particularly, and with reference to FIGS. 2 and 3, alternative ignition circuits are illustrated and differ from that in FIG. 1 in that the normally non-conducting switching means is also controlled by the charge accumulated on the capacitor. More particularly and with reference to FIG. 2, capacitor 38a is connected in series with primary coil 36a and, as in FIG. 1, across the AC. source. The capacitor is charged through rectifier 46a and resistance 48a and a four-layer diode 50 is included in a shunt circuit 40a across capacitor 38a and primary coil 36a. Four-layer diode 50 is normally nonconducting but will be rendered conductive when a particular voltage (switch-over voltage) is applied thereto. When the charge on capacitor 38a reaches a preselected value equal to the switch-over voltage of diode 50, the diode is switched to its on state and capacitor 38a discharges through diode 50 and primary coil 36a to induce the necessary voltage in secondary 34a to break down gap 14a.

The alternative ignition circuit of FIG. 3 is similar to that of FIG. 2 except that the four-layer diode has been replaced by tube 52, preferably a gas-filled tube. instance, capacitor 38b is charged through diode 46b and resistance 4812. When the charge on 38b reaches the break-down voltage of tube 52, the tube is rendered conductive and capacitor 38 discharges through primary coil 36b of transformer 32b to induce the necessary voltage in secondary 34b for ignition.

It will be appreciated that the switching means of FIGS. l-3 (the normally open switch, four-layer diode and the gas-filled tube) are all normally non-conducting and are switched to a conducting state to effect ignition.

The embodiment of FIG. 4 illustrates a still further alternative ignition circuit which may be used. More particularly, spark gap is again connected to the secondary 340 of the transformer 320. In this instance pri- In this mary 30c is connected across the AC. source with current flow through the primary being controlled by a transistor 54. A feed-back coil 56 is associated with secondary 340 so that when gap 14c is pulsed to provide ignition, a pulse is generated in coil 56. Coil 56 is connected to the base of transistor 54 and the pulse generated therein when the ignition occurs places the necessary biasing voltage on the base of the transistor to turn the transistor to its off state. After the pulse, the cut-off bias on transistor 54 is removed and the transistor is ready for conduction to produce a second pulse if necessary.

Although this invention has been illustrated and described in connection with particular embodiments thereof, it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit of the invention or from the scope of the appended claims.

What we claim is:

1. An ignition and fuel control system comprising, in combination,

electrically operated fuel flow control means characterized by having an operating voltage at which opening occurs to initiate fuel flow and a lower holding voltage at which said fuel flow control means remains open,

means for connecting said control means to an electrical source,

said fuel flow control means further characterized by said operating voltage being greater than the voltage available from said source,

means in circuit with said source and said fuel flow control means for increasing the voltage on said control means to said operating voltage to effect opening of said fuel flow control means,

means for igniting fuel,

and heat sensitive means connected in circuit with said means for increasing the voltage on said fuel flow control means and operative, in response to the flame produced by said ignition means, to remove said voltage increasing means from the circuit of said fuel flow control means to thereby reduce the voltage on said fuel flow control means below its operating voltage to said lower holding voltage.

2. An ignition and fuel control system comprising, in combination,

electrically operated fuel flow control means charac terized by having a given operating voltage a which opening thereof occurs to initiate fuel flow and a lower holding voltage at which said fuel flow control means maintains fuel flow,

ignition means for igniting the fuel supplied by operation of said fuel flow control means,

an electrical source connected to said fuel flow control means, the operating voltage of said fuel flow control means being greater than the voltage available from said electrical source and said electrical source being capable of applying at least said holding voltage to said fuel flow control means,

means in circuit with said fuel flow control means and said electrical source and operative when activated to increase the voltage applied to said fuel flow control means to said operating voltage,

and heat sensitive means connected in circuit with said voltage increasing means and arranged for response to the flame produced by said ignition means and operative, in response to said flame, to remove said voltage increasing means from the circuit of and reduce the voltage on said fuel flow control means to said lower holding voltage, whereby said fuel flow control means is connected to said electrical source for opening only in response to the combination of the voltage from said source and said voltage increasing means.

3. The combination of claim 2 wherein said ignition means is electrically operated, and wherein said heat 6 sensitive means is also connected in circuit with said ignition means and is operative to de-energize said ignition means in response to said flame.

4. An ignition and fuel control system comprising, in

combination,

electrically operated fuel flow control means charac terized by having a given operating voltage at which opening thereof occurs to initiate fuel flow and a lower holding voltage at which said fuel flow control means maintains fuel flow,

ignition means for igniting fuel supplied by said fuel flow control means, 4

a transformer connected with a source of voltage and having the secondary thereof in circuit with said fuel flow control means, said transformer operative when activated to increase the voltage applied to said fuel flow control means to said operating voltage,

and heat sensitive means to said lower holding voltage normally completing a circuit to said fuel flow control means and said transformer, said heat sensitive means arranged for response to the flame produced by said ignition and operative, in response to said flame, to open the circuit to said transformer and thereby reduce the voltage on said fuel control means.

5. An ignition and fuel control system comprising, in

combination,

electrically operated fuel flow control means including an operating coil and characterized by having a given operating voltage at which opening thereof occurs to initiate fuel flow and a lower holding voltage at which said fuel flow control means is held open,

ignition means for igniting the fuel supplied by said fuel flow control means,

a transformer connected to a source of voltage which is below said operating voltage and having its secondary in series circuit relationship with said operating coil to increase the voltage applied to said fuel flow control means to said operating voltage,

and heat sensitive means connected in circuit with said transformer and normally completing a circuit through the primary of said transformer, said heat sensitive means arranged for response to the flame produced by said ignition and operative, in response to said flame, to open the circuit to said primary and thereby de-energize said transformer to reduce the voltage on said fuel control means to said lower holding voltage.

6. An ignition and fuel control system comprising, in

combination,

a solenoid operated fuel control valve including an operating coil and having an operating voltage at which said valve is opened to initiate fuel flow and a lower holding voltage at which said valve remains open,

first and second circuit branches arranged in parallel circuit relationship with said operating coil disposed in said first branch,

a transformer connected with its primary in said second circuit branch and its secondary in said first circuit branch,

an electrical source connected to said first and second circuit branches and effective to apply at least said holding voltage but less than said operating voltage to said fuel control valve, said transformer when energized and said electrical source effective to jointly apply said operating voltage to the coil of said valve,

a normally closed flame sensor connected in said sec- 0nd circuit branch,

and ignition means for igniting fuel supplied when said valve is opened,

said flame sensor arranged for response to the flame produced by said ignition and operative, after ignition, to open said second circuit branch and de-energize said transformer and thereby reducing thevoltage on said coil to said lower holding voltage.

7. The ignition and fuel control system of claim 6 including safety switch means having thermally actuated switch means and heater means for operating said thermally actuated switch means, said thermally actuated switch means arranged between said first and second circuit branches and said heater means arranged in said second circuit branch so that operation of said safety switch means opens the circuit to said second circuit branch and leaves said first circuit branch and said heater means energized.

8. The ignition and fuel control System of claim 6 wherein said flame sensor is so arranged in circuit with said ignition means as to open the circuit to said ignition means when it responds to said flame.

9. A fuel control for a fuel burning system comprising, in combination,

electrically operated fuel flow control means characterized by having a given operating voltage at which fuel flow is initiated and below which said fuel flow control means can maintain fuel flow but cannot initiate fuel flow,

an electrical source connected to said fuel flow control means and operative to supply a voltage to said fuel flow control means below said given operating voltage and insufficient to initiate fuel flow,

means in circuit with said electrical source and said fuel flow control means and operative when activated to increase the voltage applied to said fuel flow control means from said electrical source above that available from said electrical source and to an amount sufficient to initiate fuel flow,

and means connected in circuit with said voltage increasing means and operative in response to successful ignition in said fuel burning system to deactivate said voltage increasing means and reduce the voltage on said fuel control means below said given operating voltage to a voltage sufficient to maintain fuel flow but insufiicient to operate said fuel flow control means to initiate fuel flow.

References Cited by the Examiner UNITED STATES PATENTS 1,655,742 1/1928 Scott 158-28 2,008,749 7/1935 Cunningham 15828 2,243,602 5/1941 Lange 158--28 2,623,921 12/1952 Smits 317-83 2,720,255 10/1955 Bishofberger 15828 2,743,768 5/1956 Schell 15828 2,985,797 5/1961 Williams et al 315--209 3,059,693 10/1962 Hotchkiss 158125 JAMES W. WESTHAVER, Primary Examiner. 

